a 2wd axle is wider normally than the 4x4 axle (van axles are the widest btw)but you are also throwing in the mix a different body style, as long as the spring perches are in the same spot and it has the same pinion yoke it will physically bolt in but may be wider than your current axle.

if the 04 is disk brake then you may have another issue

personally i would stay away from any g80 governor bomb unit as they were the worst thing gm ever put in a axle, there is a reason why junk yards get a premium for those axles, people that blow them up for some reason always think they need another and junk yards know it and charge more for a axle that will eventually blow up again

similar to a detroit locker, its not as forgiving as a clutch style posi so you will see more tire wear, i have heard of failures when used with tires larger than stock, not sure what kind of failure rate there really is